Conversion of free fatty acids-rich oil into biodiesel using a two-step catalytic esterification-transesterification process

  • 何 國嘉

Student thesis: Master's Thesis


In this study the low-grade oil source containing high free fatty acid content (such as waste cooking oil) to lower the cost of biodiesel production Since the waste cooking oil used has high content of free fatty acids (FFAs) which cause problems on transesterification due to saponification that consumes alkaline catalysts with free fatty acids to form soap As a consequence a two-step process was developed to solve the problems resulting from FFAs in the oil used This two-step process consists of sequential esterification and transesterification steps As for acidic catalysts used for esterification we first examined the catalytic performance of several self-developed solid acidic catalysts generated by graft acidic functional group on the different bivalent metal-based magnetic ferrites with silicon oxide shell Strontium ferrite shows the best performance among all tested ferrites on the acidic catalyst preparation Therefore the strontium ferrite-based acidic catalyst (SFA) was selected to perform the esterification experiments SFA could not only reach a FFA conversion of over 98% in 60 min of esterification but also can be recovered easily by a magnet A biodiesel production of 79 5% could be achieved after recycling the catalyst for 10 time As for the alkaline catalyst used in transesterification silicate strontium (Sr2SiO4) had an excellently catalytic reactivity as a 92% triglyceride conversion could be reached in 30 min suggesting that the Sr2SiO4 catalyst was much better for transesterification than commonly used CaO and SrO catalysts On the two-step process esterification and transesterification steps were performed separately to identify the optimum operating conditions by factorial designs with the consideration of the operating cost After that the two reactions were performed in series using simulated oil as feedstock to verify the obtained optimal operating conditions Finally waste cooking oil taken from a local stallman was used to perform an actual operation The optimum conditions for esterification by sulfuric acid and SFA were at 100oC for 60 min and at 100oC for 90 min respectively In addition the conversion of triglyceride was over 90% using both sodium hydroxide and Sr2SiO4 catalysts via transesterification reaction with an optimal condition of 60oC for 40 min regardless of oil sources used
Date of Award2014 Aug 25
Original languageEnglish
SupervisorJo-Shu Chang (Supervisor)

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